Electronic systems, such as computers, consume power during operation. Power is expensive. For a large electronic system, such as a computer server, the yearly operating cost can exceed the purchase price of the system. For a small battery powered electronic system, such as a personal digital assistant or notebook computer, the effective operating time between battery replacement or recharge is on the order of a few hours. Purchasers of large electronic systems prefer systems that are inexpensive to operate, while purchasers of small battery powered electronic systems prefer systems that have a long battery life.
Designers of electronic systems attempt to reduce the operating costs of large systems and to increase the battery life of small systems by designing circuits, such as input buffers, that operate at low voltage levels. Unfortunately, as the operating voltage levels are reduced in an electronic system, the noise margins are also reduced. Circuits operating with reduced noise margins tend to have high error rates. Thus, the problems associated with high error rates must be solved each time operating voltage levels are reduced. The problems associated with high error rates are difficult to solve and often require reducing the bandwidth of a system.
More significantly, even after system operating voltage levels are reduced, many input buffers, such as input buffers found in memory circuits, continue to consume inordinate amounts of power. Input buffers are loaded at system clock transition times, and even though each clock transition occurs over only a small portion of a clock cycle, input buffers are enabled and draw current during the entire clock cycle. So, input buffers consume power during the entire clock cycle.
For these and other reasons there is a need for the present invention.